|Easton's Bible Dictionary|
Plunder speedeth; spoil hasteth, (Isaiah 8:1-3; Comp. Zephaniah 1:14), a name Isaiah was commanded first to write in large characters on a tablet, and afterwards to give as a symbolical name to a son that was to be born to him (Isaiah 8:1, 3), as denoting the sudden attack on Damascus and Syria by the Assyrian army.
Int. Standard Bible Encyclopedia
ma'-her-shal'-al-hash'-baz (maher shalal chash baz, "the spoil speedeth; the prey hasteth"): Asymbolic name given to Isaiah's son to signify the sharp destruction of Rezin and Pekah by the Assyrian power (Isaiah 8:1, 3). Compare the Greek idea of Nemesis.
Mahershalalhashbaz (2 Occurrences)
Isaiah 8:1 Moreover the LORD said unto me, Take thee a great roll, and write in it with a man's pen concerning Mahershalalhashbaz. (KJV)
Isaiah 8:3 And I went unto the prophetess; and she conceived, and bare a son. Then said the LORD to me, Call his name Mahershalalhashbaz. (KJV)